any structural anomaly of a stellate dendritic cell of myeloid origin, that appears clear on light microscopy and has a dark-staining, indented nucleus and characteristic inclusions (Birbeck granules) in the cytoplasm; Langerhans cells are found principally in the stratum spinosum of the epidermis, but they also occur in other stratified epithelia and have been identified in the lung, lymph nodes, spleen, and thymus